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Record High Frequency Achieved

Posted by ScuttleMonkey on from the music-to-their-ears dept.

eldavojohn writes "Researchers at UCLA Henry Samueli School of Engineering and Applied Science managed to push our control of frequencies to another level when they hit a submillimeter 324 gigahertz frequency. As any signal geek out there might tell you, this is a non-trivial task. 'With traditional 90-nanometer CMOS circuit approaches, it is virtually impossible to generate usable submillimeter signals with a frequency higher than about 190 GHz. That's because conventional oscillator circuits are nonlinear systems in which increases in frequency are accompanied by a corresponding loss in gain or efficiency and an increase in noise, making them unsuitable for practical applications.' The article also talks about the surprising applications this new technology may evolve into."

6 of 141 comments (clear)

  1. Hardly the highest frequency! by oskay · · Score: 5, Informative

    Precision phase coherent control of lasers has become possible in the last ten years- Laser beams at frequencies exceeding 1 PHz (10^15 Hz) have been precisely controlled, phase locked, and tuned to have frequencies that are *exact multiples* of our best microwave frequency standards (e.g, cesium). It works the other way too-- our most precise microwave-frequency signals come from divided-down optical frequency references now! See also: 2005 nobel in physics.

    1. Re:Hardly the highest frequency! by insignificant1 · · Score: 4, Informative

      Yes, people have achieved higher frequencies, and controlled them very precisely, as you point out; however, such oscillators aren't CMOS oscillators. That's the news, that they've built a CMOS oscillator at such a frequency, not that they have achieved the highest frequency ever to be controlled (which would be a joke). Not exactly what the /. headline implies, though.

    2. Re:Hardly the highest frequency! by oskay · · Score: 4, Informative
      The work with the CMOS circuits is clearly an important achievement.

      However, both the Slashdot title ("Record High Frequency Achieved") and summary ("...managed to push our control of frequencies to another level ...") do seem imply that frequency control has not been possible at frequencies that high before. So, it's important to point out that while it's a record, it's only a record within context. (Records within context are fun; you can do anything with them. For example, I hold the bicycle land speed record for all persons with my SSN.)

      In any case, it's *not* totally different. Both are examples of frequency control, which is it's own discipline that spans precision timing and applications in all frequency ranges, from RF (on chips and in free space) to optical (on chips, in fibers, and in free space) and beyond.

  2. Re:How they did it by ToxikFetus · · Score: 5, Informative

    The researchers first generated a voltage-controlled CMOS oscillator, or CMOS VCO, operating at a fundamental frequency of 81GHz with phase-shifted outputs at 0, 90, 180 and 270 degrees, respectively. By linearly superimposing these four (or quadruple) rectified phase-shifted outputs in real time, they ultimately generated a waveform with a resultant oscillation frequency that is four times the fundamental frequency, or 324 GHz.

    This sounds a lot like a phased-lock loop. And yes, from the article, it appears as though this does have pretty good scalability. TFA said 600 GHz is achievable. 324 GHz a nice because fog is transparent at that frequency.
  3. T-rays by kebes · · Score: 3, Informative

    This technology is another step along to road to widespread technology exploiting Terahertz radiation, which is the region of the EM-spectrum between IR and microwaves. Near the end of the article, they mention the possibility of creating imaging systems that can, for example, see through clothes. These applications of so-called T-rays have in fact already been demonstrated. For example, the image in this article shows a man concealing a knife, which is easily visible in the T-ray image. (See also some other pictures here.) T-rays reflect strongly off of metals but can penetrate to varying extents through things like clothing and tissue. The military and security applications are obvious. However it would also bring up new kinds of medical imaging, and has been investigated for quality control, too (for example, scanning the inside of foods in assembly lines, etc.). In the previous link I put, there is an example of scanning through a Hershey bar, where you can see the positions of the nuts.

    Suffice it to say this is an area of active research that may have many, many applications.

  4. Sounds like extension of the push-push oscillator by MetaDFF · · Score: 3, Informative

    What they did sounds like an extension of the technique used in push-push oscillators to "double" the oscillation frequency.

    The basic principle behind a push-push oscillator is that two out-of-phase signals of fundamental frequency f_o are combined such that the fundamental signal and the odd harmonics cancel, while the second harmonic at 2*f_o add constructively. In the case of a push-push oscillator, you only need two signals 180 degrees out of phase. This could be generated with a differential VCO.

    Using a push-push oscillator is a well known technique for increasing the frequency of oscillation of a VCO beyond the fMAX of a transistors at a given process node.

    The only disadvantage with push-push oscillators is that you end up losing a lot of power as the second harmonics's power will always be much smaller than the power in the fundamental frequency of the VCO.